Now to the worrisome headline out of china tonight. That bird flu is spreading hundredsmiles from where the outbreak began. American scientists are on the ground in china worried about the mutations they have seen already. The virus has been found in beijing more than 700 miles from where it started. A 7-year-old girl has come down with it. 49 confirmed cases, 11 have died. Richard besser is in china where his former colleagues from the cdc are studying this flu. Reporter:7 years old. How did she come down with a virus. Was it from her parents who work in poultry or something else entirely? Beijing is hundreds of miles away from the outbreak. She may be a sign that this new virus can travel long distances without notice. Has the virus come by a bird or did the infected girl travel to the virus. We still don't know. It's clearly spreading with dangerous mutations. If it begins to be transmitted through people instead of birds, the outbreak would mushroom rapidly. It's easy to see why people are concerned here. Hong kong is one of the most crowded places in the world. If this virus starts to spread from person to person, you have one person sick and another and another and another. It's an absolute nightmare. Ironically the bird flu that has killed 11 people causes no illness in birds and they can't tell which ones are infected. Reporter: China may seem like it's far away but this outbreak is being taken seriously in the united states. The cdc has begun early work on a vaccine to be ready just in case this reaches our shores.

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